In many areas of process-control and energy technology the fault-free operation of a system depends on the pipelines, especially on their ability to let the relevant process medium pass through them. To avoid costly regular interruptions to operation it would be sensible to be able to detect well in advance whether a pipeline is blocked in process operation or whether the free internal cross section of the pipeline is slowly reducing. Such faults should where possible be detected right at the start, before a blockage of a pipeline can cause the plant to come to a halt. An operating fault could be avoided by a timely advance warning by optimizing maintenance processes and taking countermeasures in good time.
Previously plant operators were somewhat surprised to find that the flow though a pipeline had been suddenly blocked by a blockage. The mostly unexpected occurrence of a fault then causes production outages and the associated significant costs. One possibility of detecting a reduction in the free pipeline cross section well in advance is an endoscopic investigation of the pipeline, but this can only be done by interrupting the process and thus entails significant effort.
A method for monitoring exhaust gas transport systems with a control valve as control for a pressure-regulated exhaust emission is known from DE-PS 43 42 554. Based on the characteristic curve of the control valve at the exhaust outlet point, the pressure which would exist of the control valve were fully open is regulated as a function of the current volume stream and the regulated exhaust pressure. The maximum pressure loss occurring at maximum volume stream is determined with reference to the input pressure and the outlet pressure determined on the basis of the characteristic curve with a fully open control valve, presented as a function of time and compared with the maximum permitted pressure loss. When the value of the maximum pressure loss approaches the value of the maximum permitted pressure loss the time for cleaning the exhaust gas transport system is determined. The disadvantage of the method is that it is designed specifically for the requirements of an exhaust gas transport system and cannot simply be used as it is with other pipeline systems. In addition no account is taken of the fact that on determination of the exhaust gas pressure for a fully open control valve on the basis of its characteristic curve, because of the increased volume stream the loss of pressure over the pipeline increases additionally. The monitoring is thus comparatively imprecise.
A position regulator for a control valve with a position generator for recording the setting of the valve and with a device for evaluating the recorded position is known for example from DE 199 47 129 A1. This patent describes a system for diagnosis of the current valve status on the basis of a recorded sound signal. In particular a leakage in a closed valve is audibly detected.